Interaction of selenite with metallothionein studied by Brdika reaction

摘要

Metallothionein II (MT) is a cytosolic, ubiquitous, low-molecular-weight protein present in various tissues of mammals and non-mammals. MTs have a high content of thiol groups (-SH) which can bind mineral micronutrients and xenobiotic heavy metals. In this study, we investigated the electrode processes of MT at a mercury electrode in the presence of sodium selenite by means of the Brdika reaction in the differential pulse voltammetric mode. In Brdika solution containing ammonium buffer and [Co(NH3)(6)]Cl-3, the substance that provides catalytic reactions with proteins, interactions between MT and sodium selenite were analyzed via the hydrogen evolution catalytic signals. The reaction of -SH groups of MT with [Co(H2O)(6)](2+) complex ions on the mercury surface results into the catalytic peak Cat2. It was found that selenite ions are active in the Brdika reaction and yield also the catalytic peak of hydrogen evolution Cat2. With the increasing concentration of sodium selenite, cobalt (Co) in MT is replaced by selenium (Se). When selenite concentration increases above the MT binding capacity, i.e., MT cannot bind more Se, only selenite ions can be responsible for Cat2 signals. From our results, we conclude that Brdika reaction is a suitable method to study MT binding properties and to evaluate the influence of sodium selenite. To elucidate the experimental results a new interpretation leading to complete description of the mechanism is presented.